Ionizing shocks in argon. Part I: Collisional-radiative model and steady-state structure

Journal Article · Wed Jun 01 00:00:00 EDT 2011 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3585688· OSTI ID:21538401

Kapper, M G; Cambier, J -L ^[1]

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1. Air Force Research Laboratory, Edwards AFB, California 93524 (United States)

A detailed collisional-radiative model is developed and coupled with a single-fluid, two-temperature convection model for the transport of shock-heated argon. The model is used in a systematic approach to examine the effects of the collision cross sections on the shock structure, including the relaxation layer and subsequent radiative-cooling regime. We present a comparison with previous experimental results obtained at the University of Toronto's Institute of Aerospace Studies and the Australian National University, which serve as benchmarks to the model. It is shown here that ionization proceeds via the ladder-climbing mechanism, in which the upper levels play a dominant role as compared to the metastable states. Taking this into account, the present model is able to accurately reproduce the metastable populations in the relaxation zone measured in previous experiments, which is not possible with a two-step model. Our numerical results of the radiative-cooling region are in close agreement with experiments and have been obtained without having to consider radiative transport. In particular, it found that spontaneous emission involving the upper levels together with Bremsstrahlung emission account for nearly all radiative losses; all other significant radiative processes, resulting in transitions into the ground-state, are mostly self-absorbed and have a lesser impact. The effects of electron heat conduction are also considered and shown to have a large impact on the electron-priming region immediately behind the shock front; however, the overall effect on the induction length, i.e., the distance between the shock front and the electron avalanche, is small.

• OSTI ID: 21538401
• Journal Information: Journal of Applied Physics, Vol. 109, Issue 11; Other Information: DOI: 10.1063/1.3585688; (c) 2011 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ARGON
BENCHMARKS
BREMSSTRAHLUNG
COLLISIONS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
CONVECTION
CROSS SECTIONS
ELECTRONS
EMISSION
IONIZATION
LAYERS
LENGTH
METASTABLE STATES
PLASMA
PLASMA HEATING
RELAXATION
SHOCK WAVES
STEADY-STATE CONDITIONS
THERMAL CONDUCTION
DIMENSIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
EVALUATION
EXCITED STATES
FERMIONS
FLUIDS
GASES
HEAT TRANSFER
HEATING
LEPTONS
MASS TRANSFER
NONMETALS
RADIATIONS
RARE GASES
SIMULATION